The requirements with respect to temperature sensors and to resistors differ very significantly and consequently lead to different manufacturing processes. Thus, although a measuring accuracy of, for example, 1% leads to adequately small tolerances for resistors, in the case of Pt-100 temperature sensors with a precision of 0.1.degree. C., a measuring accuracy with a maximum 0.02% variation for a temperature stability of 0.05% is required. This accuracy, which is higher by a factor of 50, leads in the field of aligning or adjusting temperature sensors, to different new problems of which the known processes have not yet taken account. Whereas in the manufacture of resistors the heat produced by the adjustment plays little or no part, this heat generation constitutes the central problem when adjusting temperature sensors. For temperature sensors with an accuracy in the indicated range of 0.01.degree. C. after manufacture, it is necessary to provide a thermostat with a high thermal stability, i.e., a divergence of less than 0.05.degree. C. and wherein, due to the high accuracy requirement, there is no air movement and no entry of light.
Laser adjusting devices of the prior art measure the resistance of the temperature sensor during trimming and therefore are not suited for commercial purposes. All standard methods contain a step-by-step trimming and measurement, i.e., steps of measurement, partial trim, measurement again, further trim, etc., during adjustment which needs a lot of time. This aspect is very important in connection with high volume commercial production applications. If there is only one temperature sensor to adjust, it would not be so important if the temperature stabilization of the substrate with the sensor takes, for example, 10 seconds before the "trimming-measurement" process may be started and the process itself takes maybe 50 seconds. But if there are 100 or 200 temperature sensors to trim an adjustment of the sensors one after another would take hours.
Furthermore, many modern applications with temperature sensors require very small sensors. Thus, the dimensions of the trimming path should be as small as possible. It is not possible to adjust such narrow trimming paths with functional adjustment in a satisfactory manner. Even if some known methods use a digital trimming in a first step a subsequent second step for fine trimming is required. For this reason, these methods using a "widened part" for analog adjustment lead to a compromise between the size of the sensor and its precision.